1. Field of the Invention
This invention relates to an undersea release apparatus for releasing underwater devices, and more particularly to an improved release mechanism which operates reliably in the face of the adverse environmental conditions encountered at both shallow and full ocean depths, including extreme hydrostatic pressures.
2. Brief Description of the Prior Art
Recovering previously deposited underwater devices from the ocean floor requires the use of a release mechanism attached to an anchor by means of a connecting link fixedly attached to the anchor and releasably attached to the bottom of the underwater device. The release may be effected by an external latch on the outside of the underwater device and driven to an unlatched position by electromechanical components within the underwater device. For example, in an undersea acoustic transponder device, a signal can be transmitted by the recovery ship, and apparatus within the transponder, upon receiving the appropriate transmitted command code, moves the external latch to its unlatched position so as to permit the link to be released from the anchor, allowing a floatation assembly, connected to the top of the underwater device, to transport the underwater device to the surface. In the past, however, the mechanisms designed for unlatching the link from the anchor have been ineffective for a variety of reasons.
First, full ocean depth mechanical or electro-mechanical release mechanisms may be subject to extreme deep ocean hydrostatic pressures, resulting in correspondingly high frictional drag on any moving part of the latch mechanically actuated from within the underwater device. A rotating shaft penetrating the top plate of an undersea device, for example, exhibits very large frictional drag against bushings separating the cap of the shaft from the top plate, even when using bushings having a low friction coefficient. Secondly, sand, debris, as well as biological growth can prevent release of the link from the release mechanism, especially if the underwater device has been deployed for a number of weeks or months.
One prior art solution to the unreliable release problem is the provision of an elongated pivotal pelican hook which has its upper end latched by the latch mechanism and its lower end capturing the link between the curved end of the hook and a slotted frame member of the underwater device. Upon release of the top of the pelican hook, a downwardly directed force on the connecting link by the weight of the anchor (due to the buoyancy of the floatation assembly pulling the underwater device upwardly) applies pressure to the bight portion of the hook which pressure is intended to be sufficient to pivot the pelican hook about its axis and free the link by moving the hook portion out of the slot of the frame. Again, however, because of the frictional drag between the bight portion of the pelican hook and the bottom side of the link, the friction at the hook/frame pivot points, and debris which may have accumulated at the pivot points or at the release point at the bottom of the pelican hook, there may be insufficient force against the hook by the link to pivot the hook out of its blocking position with respect to the frame, and the underwater device cannot be released and recovered. In such an adverse environment, even reliably operating an unlatching mechanism to release the top of the pelican hook is a problem, aside from the separate problem of pivoting the pelican hook after its release. The release problems with such an arrangement of the prior art become even more acute when the considering that, in some instances, the positive buoyancy of the floatation assembly may be, deliberately, small, and therefore the force exerted by the floatation assembly is often insufficient to effect reliable release of the device. One solution to this problem is to increase the offset between the hook/link contact point and the hook pivot axis to give greater leverage in pivoting the hook. However, this requires greater latching forces which must be overcome by the release mechanism, compounding the release problems.
Another prior art undersea release apparatus uses a hollow rotatable cylindrical element which has sloping curved cutouts on its opposing walls for positively driving a pivot pin a small distance. This movement is intended to release the capture of the end of a pivoting arm so that the arm can pivot and thereby release the connecting link between the anchor and the underwater device. However, as with the other prior art device described above, simply unlatching a pivoting arm does not necessarily guarantee that the arm will pivot, again due to the influencing factors of high hydrostatic pressure and fouling by debris and growth.
Other prior art release apparatuses are known which vary only in the manner in which the element capturing the connecting link is released. In all such prior art apparatuses, when the adverse conditions are severe enough or are combined, all such prior art apparatuses will fail for the reasons described above with respect to the specific examples of prior art arrangements.
There is therefore a recognized need in the art to provide an undersea release apparatus which reliably releases the connecting link from a deployed underwater device in the face of extreme adverse environmental conditions. The present invention provides such an apparatus.